Ad marks for leona?

Only if AD stands for Armor Defense Reds

Standard for basically every support

For any support that autoattacks ever, armor pen or hybrid pen is generally the norm. I'd go ar.pen on Leona I think. Depends on how often you poke with W or E/Q combo. Mostly E/Q: armor pen. Mostly W: magic pen. 50/50: hybrid pen. Flat AD doesn't sound very useful on her. Generally flat ad is only good if you get some kind of AD scaling on a skill. Like Ezreal Q gets 110% AD scaling, meaning your 8.5 bonus ad from flat ad marks will make q's do something around 9 extra damage, plus extra on the autoattacks too. Might not sound like much but just having a -little bit- more than the other guy can sometimes mean the difference in snowballing them out of lane or them escaping with 10 hp. But with Leona she gets 0% ad scaling on anything, so you'll only do the extra damage on autoattacks, and armor/magic pen will usually win out in small trades or disable their armor seals/MR glyphs

Edit: Should add that if you go full armor pen marks you need to throw in a couple extra auto attacks in there for it to be as effective/better than magic pen. Can't just E/Q/auto with q charged and walk away. Something closer to E in, autoattack, Q to reset autoattack timer, auto again, then auto one more time while stunned. It gives their support/whoever you didn't stun with the q, time to hit you back...but...you are Leona..so, you can usually take a couple hits for the team. ;)

i love running flat ad on all my supports. the enemy adc usually dont expect the extra damage i have until i bash their face into the fountain with my shield

For her and most tanks/tank supports I usually use

AD Marks Health Seals Scaling MR Glyphs Armor Quints

So yeah AD Marks work pretty well.

I run AD marks on ranged supports. leona/Taric I run armor marks, armor quints, and 4 armor seals + 5 scaling health seals. Idk. Works for me. Tanky as fuck. Helps tower dives early.

Personally, I prefer the IDGAF route for melee tank supports like or :

Armor Marks (because each gives 0.91 Armor, which is almost as good as Armor Seals) A mix of HP and HP/level Seals (Stronger than Armor if you have Armor Reds, imo) MR/lvl Glyphs Armor Quints (at 4.26 Armor a piece, those are worth 4.26 Armor Seals each. Most efficient source for Armor in runes).

21 Armor from runes.

Masteries, if I really want to go over the top with Leona, 0/21/9. 5 Armor + 8 in a duolane, +5% extra bonus Armor 21 + 8 + 5 = 34 * 1.05 = 36 bonus Armor on level 1.

63 Armor level 1? No problem. At that point, you can pretty much ignore the enemy's auto-attacks.